Note: Descriptions are shown in the official language in which they were submitted.
CA 02294156 2006-02-08
30194=4
1
ELECTROMAGNET SYSTEM AND METHOD FOR JOINING CORE AND YOKE IN
SUCH A SYSTEM
FIELD OF THE INVENTION
The invention is directed to an electromagnet
system with a yoke and a core that has a fastening end
secured in a round hole of a yoke section, whereby the core
comprises a preferably cylindrical shaft and a cone section
expanded toward its fastening end, this latter having a core
diameter exceeding the diameter of the round hole
penetrating the material of the yoke. The invention is also
directed to a method for joining core and yoke given such a
system.
BACKGROUND OF THE INVENTION
EP 0 593 517 B1 discloses an electromagnet system
of the species initially cited wherein the core has its
cylindrical shaft plugged through a round hole of the yoke
leg proceeding from the outside and has the core section of
its end side clamped in a bore of the yoke leg. For
clamping and for setting the final position, the core is
thereby charged with pulse-like impacts. Although a good
interference seat of the core derives in this way, the
pulse-like impacts can produce undesired jolts and friction
at other elements connected to the magnet system, for
example at contacts. Moreover, the adjustment of the core
therein is possible only in one direction, namely in the
direction of the core insertion.
DE 31 48 052 A1 also already discloses an
electromagnetic relay whose coil core is secured with a fine
thread in a bore likewise correspondingly provided with a
fine thread, being secured and adjusted by being screwed in.
This exact screw connection, however, not only requires
CA 02294156 2006-02-08
30194=4
1a
complicated manufacture and assembly of the parts but it by
itself also does not produce an adequate interference fit,
so that additional fixing means are required. For example,
it is thus proposed to apply a plastic adhesive onto the
fine thread or to provide the core with an additional
counter-nut for securing. This requires an additional
outlay; further, the fixing agent in the thread can
deteriorate the magnetic coupling, whereas the additional
counter-nut also requires additional space.
A goal of the invention is to improve an
electromagnetic system of the species initially cited such
that a good and dependable connection and magnetic
OCT-18-99 13:18 3128767052 P.13 R-791 Job-703
OCT, -18'~99(MON) 12.20 HILL LAW FIRM TEL:3128767052 P, 013
coupling of core and yoke is achieved in a simple way, whereby this connection
should be capable of being exactly adjusted - namely both forward as well as
backward.
This goal is inventively achieved in that a thread is fashioned on the
conical section of the core, said thread being fumed self deforming into the
inherently
thread-free wall of the likewise comically expanded recess of the yoke.
Given the invenfiive magnetic system, thus, the conical section of the core
and the conical inside wall of the round hole in the yoke section are already
matched
to one another. The ultimate fastening in one another and the fine
positioning,
Z 0 however, ensue by turning via the thread fashioned on the cone section of
the core,
this digging into the smooth inside surface of the round hole when turned in.
rt is
comparatively simple to manufacture this one thread on the core since a mating
with a
correspondingly pre,fabrieated, complementary nut thread in the yoke is not
required.
Due to the displacement of the material when the thread core is screwed into
the yoke
section, an excellent interference scat as well as a good magnetic coupling
between
these two parts derive without auxiliary measures. An especially good coupling
derives when the thread an the core is fashioned as flat thread, (i.e. when
the
individual turns of the thread channel or, respectively, of the thread
channels given
raultiple-start threads) exhibit a large spacing in relationship to the
channel depth, so
2 0 that a flattened thread web arises that is trapezoidal in cross section or
approximately
saw-tooth-shaped given a sidewall that is steeper at one side.
The cone section of the core and the conical inside wall of the round hole
in the yoke can, for example, have an angle between 0.5° and 5°
relative to the core
axis. However, an angle similar to conical sleeves and conical shafts for self
locking
2 5 tool fastening is preferably selected. The angle of the cone envelope
relative to the
axis thereby lies between 1° aad 2°, preferably at approximately
1.5° (1° 30 minutes)
or, respectively, between 1 ° 25 minutes and 1 ° 30 minutes in
what is referred to as a
Morse cone. Given this slight slope angle, it would also be conceivable to
fashion
that shat of the core with the fastening section continuously slightly
comically (with
CA 02294156 1999-12-17
CA 02294156 2006-02-08
30194=4
3
approximately 1° slope). The thread can be especially
simply produced on the cone section when the thread channel
or, respectively, thread channels exhibits (or,
respectively, exhibit) a constant inside core diameter.
This means that the thread has not been or has only been
slightly dug in at the narrowest location of the cone
section wherein it is cut in deeper and deeper toward the
broadened end. An especially simple manufacture and
processing derives given fashioning as rolling thread.
For improving the magnetic properties, both the
yoke as well as the core are expediently soft-annealed. The
soft-annealed yoke also has the advantage that it easily
widens or, respectively, deforms when the threaded core is
turned in, that excessively high torques are not required.
It is advantageous at the core when it is annealed before
the thread is rolled on, since the warp [sic] at the thread
walls produced by material displacement when rolling the
thread experiences a certain hardening and thus digs more
easily into the soft-annealed, thread-free material of the
round hole when the core is turned in.
Moreover, a surface coating of copper or copper-
graphite can facilitate the turning and prevent ceasing.
This can ensue nearly without additional outlay since a
coating, for example with Cu, is desirable anyway as
corrosion protection. The thread proceeds partly only in
the coating, which serves as a type of lubrication.
An inventive method for joining core and yoke in
an electromagnet system, characterized by the following
steps: producing a conical round hole in a yoke;
manufacturing a core with a cylindrical shaft and a conical
section expanded toward a free end; producing a thread on
the conical section; plugging the cylindrical shaft of the
CA 02294156 2006-02-08
30194=4
4
core through the round hole of the yoke until the conical
section ceases in the round hole; and turning the core in
thread direction upon application of an axial force until
the free end of the cylindrical shaft has reached a
predetermined position.
According to one aspect of the present invention,
there is provided an electromagnet system comprising: a
yoke having a transverse section with a round hole therein
with a conically tapered entrance with a smooth surface; a
core having a core body comprising an integrally formed
cylindrical shaft and fastening end, said fastening end
having an outwardly conical section, the core being inserted
in the round hole of the transverse section of the yoke with
the end distal to the fastening end being inserted first, at
least a portion of the conical section being larger in
diameter than the round hole, said portion of the conical
section being proximate to the fastening end, the conical
section being threaded and engaging the smooth surface of
the entrance of the round hole of the transverse section of
the yoke.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in greater detail below
with reference to an exemplary embodiment on the basis of
the drawings. Shown are:
Figure 1 a double relay with two coupled,
inventive magnet systems;
Figures 2 and 3 a partially cut core of a magnet
system according to Figure 1 in a perspective illustration
and in a side view;
CA 02294156 2006-02-08
30194=4
4a
Figure 4 an enlarged detail excerpt IV from
Figure 3; and
Figure 5 the same excerpt as Figure 4 but with a
modified thread shape.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
The double relay shown in Figure 1 has two magnet
systems each having a respective yoke 1 that has a
longitudinal section 11 and a transverse section 12. A core
having a round cross section is secured in each of the
transverse yoke sections 12, this core 2 to be described in
detail later. Each of these cores 2 has a pole end 21
having a pole surface 22 that forms a working air gap
together with an armature 3. In the example of a double
relay shown in Figure 1, the two longitudinal yoke legs 11
are connected to one another of one piece, and the shared
armature 3 interacts with the two cores 2 in alternation.
It follows from this example that, in such a case, the core
can only be mounted by being plugged from the outside
through the yoke leg 12. Otherwise, however, the invention
could also be applied in the same way for a simple relay
having only one yoke and one core.
In a known way, the illustrated double relay also
has a coil body 4 as carrier for two windings 5 as well as
contact springs 6 and fixed contacts 7. This relay
structure is known in and of itself and need not be
discussed in greater detail in conjunction with the present
invention.
The coil core 2 has a respective fastening end 23
secured in a round hole 13 of the transverse yoke leg 12.
This round hole 13 is comically expanded from inside toward
outside (from the coil) in adaptation to the core 2 and is
CA 02294156 2006-02-08
30194=4
4b
matched to the diameter of the core such that the
penetration described below yields a good interference seat
and a good magnetic coupling.
According to Figures 2 and 3, the core 2 has a
cylindrical shaft 24 whose diameter is somewhat smaller than
the narrowest diameter of the round hole 13, so
OCT-19-98 13:16 3126767052 P.16 R-791 Job-703
OGT.-18'99(MON) 12.21 HILL LAW FIRM TEL:3128767052 P.016
that it can be easily plugged into the coil from the outside through the yoke
section
12. The core 2 also has a cone section 25 that comically expands toward the
fastening
end 23. Toward the end, the pitch exhibits an angle a relative to the axis of
the core
that can lie approximately between 0.5° and S°. Preferably,
however, this angle - as
5 already mentioned - will lie between 1 ° and 2°. The round
hole 13, moreover,
comprises approximately the same pitch. 'Vhhereas, however, the inside surface
of the
round hole 13 is kept smooth, a. rolling thread is fashioned on the thread
section 25,
the thread web 27 thereof comprising a flattened upper side. This can be
clearly seen
in Figure 4, which shows an enlarged illustrated of the detail IV in Figure 3.
It can be
1 o seen therefrom, that the depth of the thread channel 26 is so slight
compared to the
thread slope s (given a single-pitch thread) that the thread web 27 comprises
a
flattened upper side 2B, i.e. exhibits a trapezoidal cross section according
to Figure 4.
The inside diameter of the thread is preferably kept smooth for manufacturing
reasons, so that the thread channel 26 does not dig into the surface or digs
only
slightly into the surface at the beginning of the cone section 25 - i.e., at
the smallest
diameter thereof -, whereas this channel becoiues deeper and deeper toward the
cad
23. Instead of the illustrated, single-pitch thread, a rnulti-pitch thread
could also be
provided. According to Figure 4, the thread channel 26 has au aperture angle y
of
approximately 60°, whereby the width of the surface 28 of the thread
web 27 (in the
2 0 proximity of the end 23) amounts to approximately half the slope s.
However, other
relationships are also possible. For example, as shown in the modification
according
to Figure 5, a thread cross section in the form of a flatted saw tooth can be
provided. In this case, too, the thread web 27 bas a flattened upper side 28
that, for
example, again exhibits a width in the proximity of the end 23 that
corresponds to
2 5 approximately half the thread slope s. In the region of the smaller cone
diameter, of
course, the thread web is even wider, since the thread channel exhibits less
of a depth
d thereat. For turning the core 2 into the round hole 13, a hexagonal recess
is
centrally applied proceeding from the fastening end 23, this enabling the
placement of
CA 02294156 1999-12-17
OCT-i6-99 13:18 3128767052 P.17 R-791 Jab-703
OCT,-18'99(MON) 12:21 HILL LAW FIRM TEL:31287b7052 P,017
s
a taming tool. Of course, some other, arbitrary shape that enables the
placement of a
screwing foul could also be selected instead of the hexagon.
Given manufacture of the magnet system, the round hole I3 is preferably
first pre-shaped by a punch needle and is subsequently calibrated with a
conical pin
far forming a conical expansion. The yoke is subsequently so$-annealed in
order to
generate uniform magnetic properties and to prescribe a certain yield when
turning the
care in.
In a standard way, the core is manufactured with the cylindrical Shaft 24
and the cone projection 25 as well as the hexagonal recess 29. It is then
likewise soft-
annealed and subsequently conducted through a thread rolling device, where the
flat
thread that has already been described is rolled onto the cant section 25, As
a result
of the rolling process, small warps [sick 30 arise at the sidewalk of the
thread web 27
due to material displace~uent. These warps 30 experience a alight hardening
and
thereby improve the penetration of the thread into the thread-&ec, inside
surface of the
round hole 13 when the core is turned in.
The core 2 that has been prepared in this way is, as already mentioned,
plugged through the round hole 13 from the outside until the cone section 25
has its
thread ceasing in the round hole I3. Subsequently, it is farther in with a
suitable turning tool and upon application of a certain axial force, whereby
the thread
2 o digs into the material of the yoke. 8y being horned, the core can thus be
very exactly
positioned in axial direction relative to the armature, whereby the thread
also enables
a certain backward adjustment by reverse turning. In any case, a good
interference fit
of the core in the yoke and a good magnetic coupling between the core and the
yoke
are assured in this way,
CA 02294156 1999-12-17
